A scanning transmission electron microscope (STEM), a transmission electron microscope (TEM), or the like is used to observe the internal structure of an object in a minute region. A known general method for observing the interior of a specimen by using such an electron microscope is arranging a specimen that is thinly sliced such that an electron beam can be transmitted therethrough on a specimen base on a mesh that is provided with multiple holes and obtaining a transmitted electron beam with a detector that is arranged on the opposite side of a specimen face from the source of electrons. Furthermore, a method of obtaining transmission electron microscope images in various directions by tilting the specimen has recently drawn attention in the field of materials science, medical science, and biology as a method for observation of the three-dimensional internal structure of an object. In PTL 1, there is suggested a method of finding a three-dimensional positional arrangement by tilting the specimen.
Not only an electron microscope, but also an optical microscope can be used to observe the internal structure of an object. By using an optical microscope, it is possible to obtain color information that cannot be obtained with an electron microscope. As a method for preparing a specimen for optical microscopic observation, wide use has been made of a method in which observation is performed by placing a specimen that is thin enough to allow transmission of light on a flat base such as a slide glass or by applying a liquid-state specimen onto the base or of such a method.